In this study, the seasonal variation in Aeolus wind product performance over China is analyzed by using L-band radiosonde detection data and ERA5 reanalysis data. The results show that the Aeolus wind product performance is affected by seasonal factors, which may be caused by seasonal changes in wind direction and cloud distribution.

We present experimental proofs illustrating the emission of an unexplored volatile organic compound, tentatively assigned as ketene, in an industrial facility in South Korea. The emission of such a compound has rarely been reported, but our experimental data show that the emission rate is substantial. It potentially has tremendous implications for regional air quality and public health, as it is highly reactive and toxic at the same time.

Severe ozone pollution frequently occurred in North China and obviously damages human health and ecosystems. The meteorological conditions effectively affect the variations in ozone pollution by modulating the natural emissions of O₃ precursors and photochemical reactions in the atmosphere. In this study, the interannual relationship between ozone-related meteorology and late-spring snow cover in West Siberia was explored, and the reasons of its decadal change were also physically explained.

We present the first estimate of ozone enhancement by fire emissions through ozone–vegetation interactions using a fully coupled chemistry–vegetation model (GC-YIBs). In fire-prone areas, fire-induced ozone causes a positive feedback to surface ozone mainly because of the inhibition effects on stomatal conductance.

This work targets the chemical composition of α-pinene-derived secondary organic aerosol (SOA) formed in the temperature range from -15 to 20°C. Experiments were conducted in an atmospheric simulation chamber. Positive matrix factorization analysis of data obtained by a high-resolution time-of-flight aerosol mass spectrometer shows that the elemental aerosol composition is controlled by the initial α-pinene concentration and temperature during SOA formation.

Aircraft in situ observations of low-level Beaufort Sea cloud properties and thermodynamics from the ARISE campaign are compared with the Arctic System Reanalysis (ASR) to better understand deficiencies in simulated clouds. ASR produces too little cloud water, which coincides with being too warm and dry. In addition, ASR struggles to produce cloud water even in favorable thermodynamic conditions. A random sampling experiment also shows the effects of the limited aircraft sampling on the results.

Sunlight affects the life and chemical composition of atmospheric aerosols and thus alters air quality. This study demonstrated that the photo-aging process not only changed the chemical compositions of chromophoric aerosols but also changed the roles of the chromophoric organic matter in the photo-aging process of aerosol. This study adds to our understanding of how sunlight affects chromophoric aerosol aging.

Typhoons above the Northwest Pacific frequently lead to severe ambient ozone pollution in the Pearl River Delta, China, in autumn and summer. However, typhoons do not enhance ozone transport, production and accumulation at the same time, and differences also exist between these influences in two seasons. Through systematic comparisons, we revealed the complex interactions between local meteorology and ozone processes, which is essential for understanding the causes of regional ozone pollution.

Ice-nucleating particles (INPs) are not well characterized in the Arctic despite their importance for the Arctic energy budget. Little is known about their nature (mineral or biological) and sources (terrestrial or marine, long-range transport or local). We find indications that, at the beginning of the melt season, a local, biogenic, probably marine source is likely, but significant enrichment of INPs has to take place from the ocean to the aerosol phase.

We explored molecular properties affecting atmospheric particle formation efficiency and derived a parameterization between particle formation rate and heterodimer concentration, which showed good agreement to previously reported experimental data. Considering the simplicity of calculating heterodimer concentration, this approach has potential to improve estimates of global cloud condensation nuclei in models that are limited by the computational expense of calculating particle formation rate.

This paper shows the first multisite online measurements of PM₁ in Delhi, India, with measurements over different seasons in Old Delhi and New Delhi in 2018. Organic aerosol (OA) source apportionment was performed using positive matrix factorisation (PMF). Traffic was the main primary aerosol source for both OAs and black carbon, seen with PMF and Aethalometer model analysis, indicating that control of primary traffic exhaust emissions would make a significant reduction to Delhi air pollution.

The result shows dust aerosols from the Taklimakan Desert have higher aerosol scattering during dust storm cases of this paper, and this caused higher negative direct radiative forcing efficiency (DRFEdust) than aerosols from the Sahara. The microphysical properties and particle shapes of dust aerosol significantly influence DRFEdust. The satellite-based equi-albedo method has a unique advantage in DRFEdust estimation: it could validate the results derived from the numerical model directly.

In July and August 2017, eight StratoClim mission flights of the Geophysica reached up to 20 km in the Asian monsoon anticyclone. New particle formation (NPF) was identified in situ by abundant nucleation-mode aerosols (6–15 nm in diameter) with mixing ratios of up to 50 000 mg⁻¹. NPF occurred most frequently at 12–16 km with fractions of non-volatile residues of down to 15 %. Abundance and productivity of observed NPF indicate its ability to promote the Asian tropopause aerosol layer.

Clouds cool our atmosphere. The role of small aerosol particles in affecting them represents one of the largest uncertainties in current estimates of climate change. Traditionally it is assumed that cloud droplets only form particles of diameters ~ 100 nm (accumulation mode). Previous studies suggest that this can also occur in smaller particles (Aitken mode). Our study provides a general framework to estimate under which aerosol and cloud conditions Aitken mode particles affect clouds.

This study introduces the in situ CO₂ measurement system installed in Beijing (urban), Xianghe (suburban), and Xinglong (rural) in North China for the first time. The spatial and temporal variations in CO₂ mole fractions at the three sites between June 2018 and April 2020 are discussed on both seasonal and diurnal scales.

The variability, sources, and transport of ethane (C₂H₆) over eastern China from 2015 to 2020 were studied using ground-based Fourier transform infrared (FTIR) spectroscopy and GEOS-Chem simulations. C₂H₆ variability is driven by both meteorological and emission factors. The reduction in C₂H₆ in recent years over eastern China points to air quality improvement in China.

We present results from PM₁ atmospheric composition and concentration measurements performed in a springtime hemiboreal forest. Sesquiterpene mixing ratios and particle-phase concentrations of corresponding oxidation products were rapidly increasing on some early mornings. The particle volatility suggested that condensable sesquiterpene oxidation products are rapidly formed in the atmosphere. The results revealed the importance of sesquiterpenes for secondary organic aerosol particulate mass.

Alkali feldspar is the most abundant mineral in the Earth's crust and is often present in mineral dust aerosols that are responsible for the formation of rain and snow in clouds. However, the cloud droplets containing pure potassium-rich feldspar would not freeze unless cooled down to a very low temperature. Here we show that partly replacing potassium with sodium would induce fracturing of feldspar, exposing a crystalline surface that could initiate freezing at higher temperature.

The sources and seasonal trends of water-soluble organic carbon (WSOC) in PM_2.5 on long-term trends at two sites in Japan are investigated by carbon isotope ratio (δ¹³C) of WSOC. At the rural site, the δ¹³C of WSOC from autumn to spring was concluded to reflect mainly the biomass burning of rice straw. The heaviest δ¹³C of WSOC from February to April 2019 might reflect long-range transport of particles resulting from the overseas burning of C₄ plants such as corn.

Iodine plays a vital role in oxidation chemistry over Antarctica, with past observations showing highly elevated levels of iodine oxide (IO) leading to severe depletion of boundary layer ozone. We present IO observations over three summers (2015–2017) at the Indian Antarctic bases of Bharati and Maitri. IO was observed during all campaigns with mixing ratios below 2 pptv, which is lower than the peak levels observed in West Antarctica, showing the differences in regional chemistry and emissions.

We present a comparison of the changes to light absorption behavior and chemical composition of wildfire smoke particles from day- and nighttime oxidation processes and discuss the results within the context of previous laboratory findings.

Air–sea processes are key elements during Mediterranean heavy precipitation events. We aim to progress in their representation in high-resolution weather forecast. Using coupled ocean–air–wave simulations, we investigated air–sea mechanisms modulated by ocean and waves during a case that occurred in southern France. Results showed significant impact of the forecast on low-level dynamics and air–sea fluxes and illustrated potential benefits of coupled numerical weather prediction systems.

This paper investigates the impact of global warming on heat and humidity extremes. There are three major findings in this study. We quantify how unforced variability in the climate impacts can lead to large variations where heat waves occur, we find that all heat extremes increase as the climate warms, especially between 1.5 and 2.0 °C of the average global warming, and we show that the economic inequity of facing extreme heat will worsen in a warmer world.

Formation of new particles is a key process in the atmosphere. New particle formation events arising from nucleation of gaseous precursors have been analysed in extensive datasets from 13 sites in five European countries in terms of frequency, nucleation rate, and particle growth rate, with several common features and many differences identified. Although nucleation frequencies are lower at roadside sites, nucleation rates and particle growth rates are typically higher.

Our results suggest that lightning strokes would probably influence the ionosphere and thus give rise to the occurrence of a sporadic sodium layer (Na_S), with the overturning of the electric field playing an important role. Model simulation results show that the calculated first-order rate coefficient could explain the efficient recombination of Na⁺→Na in this Na_S case study. A conjunction between the lower and upper atmospheres could be established by these inter-connected phenomena.

For decades, high concentrations of ice observed in precipitating mixed-phase clouds have created an enigma. Such concentrations are higher than can be explained by the action of aerosols or by the spontaneous freezing of most cloud droplets. The controversy has partly persisted due to the lack of laboratory experimentation in ice microphysics, especially regarding fragmentation of ice, a topic reviewed by a recent paper. Our comment attempts to clarify some issues with regards to that review.

This study analyzes the microphysical characteristics of snow in complex terrain and the nearby ocean according to topography and wind pattern during the ICE-POP 2018 campaign. The observations from collocated vertically pointing radars and disdrometers indicate that the riming in the mountainous region is likely caused by a strong shear and turbulence. The different behaviors of aggregation and riming were found by three different synoptic patterns (air–sea interaction, cold low, and warm low).

In this paper, a novel method for retrieving cloud base height and geometric thickness is developed and applied to produce a global climatology of boundary layer clouds with a high accuracy. The retrieval is based on the 333 m resolution low-level cloud distribution as obtained from the CALIPSO lidar data. The main part of the study describes the variability of cloud vertical geometrical properties in space, season, and time of the day. Resultant new insights are presented.

In this study, we conducted laboratory studies to investigate the formation of gas-phase highly oxygenated organic molecules (HOMs). We provide a thorough analysis on the importance of multistep auto-oxidation and multigeneration OH reactions. We also give an intensive investigation on the roles of high-NO₂ conditions that represent a wide range of anthropogenically influenced environments.

This paper shows how aerosol hygroscopicity enhances the vertical profile of aerosol backscattering and extinction. The study is possible thanks to the large set of remote sensing instruments and focuses on the the Baltimore–Washington DC metropolitan area during hot and humid summer days with very relevant anthropogenic emission aerosol sources. The results illustrate how the combination of aerosol emissions and meteorological conditions ultimately alters the aerosol radiative forcing.

Cold air outbreaks affect the local energy budget by forming bright boundary layer clouds that, once it rains, evolve into dimmer, broken cloud fields that are depleted of condensation nuclei – an evolution consistent with closed-to-open cell transitions. We find that cloud ice accelerates this evolution, primarily via riming prior to rain onset, which (1) reduces liquid water, (2) reduces condensation nuclei, and (3) leads to early precipitation cooling and moistening below cloud.

Interactions of extreme fires with weather systems can produce towering smoke plumes that inject aerosols at very high altitudes (> 10 km). Three such major injections, largest at the time in terms of emitted aerosol mass, took place over British Columbia, Canada, in August 2017. We model the transport and impacts of injected aerosols on the radiation balance of the atmosphere. Our model results match the satellite-observed plume transport and residence time at these high altitudes very closely.

Our work investigates the diurnal evolution of atmospheric ammonia concentrations during a major pollution event. It analyses it in regard of both chemical (gas–particle conversion) and physical (vertical mixing, meteorology) processes in the atmosphere. These mechanisms are key for understanding the evolution of the physicochemical state of the atmosphere; therefore, it clearly fits into the scope of Atmospheric Chemistry and Physics.

The wind shear generated on a local scale by the diversified relief’s impact can be a factor which significantly modifies the spatial pattern of PM₁₀ concentration. The vertical profile of PM₁₀ over a city located in a large valley during the events with high surface-level PM₁₀ concentrations may show a sudden decrease with height not only due to the increase in wind speed, but also due to the change in wind direction alone. Vertical aerosanitary urban zones can be distinguished.

In this study, we found that the aqueous solution in aerosols is an important absorbing phase for gaseous polyols in the atmosphere, indicating that the dissolution in aerosol liquid water should not be ignored when investigating gas–particle partitioning of water-soluble organics. The exponential increase in effective partitioning coefficients of polyol tracers with sulfate ion concentrations could be attributed to organic–inorganic interactions in the particle phase.

New particle formation (NPF) occurred dominantly in the Antarctic free troposphere during spring and fall and in the free troposphere and boundary layer during summer. With the existence of the ozone hole, more UV radiation can enhance formation of aerosol precursors and NPF in the free troposphere. Here, we assess the hypothesis that UV enhancement in the upper troposphere by the Antarctic ozone hole modifies the aerosol and cloud properties in Antarctic regions during summer.